1. Field of the Invention
The present invention relates to the cleaning of boat tanks, bilges, and holds; barges; mobile or land based tanks: cutting boxes or container; and related vessels (sometimes hereinafter referred to as "vessels") that have been contaminated with oil and gas well drilling fluids such as oil well drilling mud and the like or with hazardous waste. More particularly, the present invention relates to a method and apparatus for the cleaning (in a marine and land based environment) of vessels that have been contaminated with oil and gas well drilling fluids, wherein a recycling water recovery system reuses the same wash water over and over, while continuously concentrating solid material in a receiving barge after the wash water leaves the vessel being cleaned and carrying oil and gas well drilling fluid waste products therewith (including solid material), and wherein various treatment stations remove solid material, oil, and like pollutants from the wash water stream before it is recycled to clean the vessel a second time or to clean a second vessel or a third vessel, etc.
2. General Background
In the drilling of oil and gas wells, there are a number of fluids that are used in the drilling process. These fluids include for example drilling mud that contains heavy solids. This drilling mud becomes a pollutant when it is placed in a vessel that is used to transport drilling mud from land to oil and gas well and drilling production platforms located offshore.
Other oil and gas well drilling, completion and work over fluids include non-dispersed drilling mud, dispersed drilling mud, calcium treated drilling mud, drilling mud incorporating polymers, drilling muds prepared from fresh or brine water and sodium chloride, oil-based drilling mud and synthetic drilling mud. Other fluids used in the drilling of oil and gas wells include bactericides, calcium removers, corrosion inhibitors, defoamers, emulsifiers, filtrate reducers, flocculants, foaming agents, lost circulation materials, lubricants, pipe-freeing agents, shale control inhibitors, and surface active agents. A discussion of the various types of drilling, completion and workover fluids used in the oil and gas well drilling industry can be seen in the June 1994 issue of "World Oil".
Additionally, drilling fluids not used downhole in the drilling process or discarded hydrocarbon based waste fluids that have to be transported back to land are considered hazardous waste as defined by the United States Environmental Protection Agency.
The present method of cleaning such oil and gas well drilling fluids and hazardous waste from vessels is to simply wash the vessel while capturing the wash water in a barge. The wash water becomes contaminated with the oil and gas well drilling fluids and hazardous waste. The barge must then be shipped to a disposal site wherein the contaminated wash water is disposed of.
The disposal of a barge filled with wash water from such a vessel cleaning operation is an expensive and time consuming procedure. Each barge contains thousands of gallons of contaminated wash water and may have to be transported with a tug vessel to a disposal site.